Air-pressure-operated relay



Feb. 17, 1959 2 Sheets-Sheet 1 Filed Jan. 11, 1954 FIG.

INVENTOR. ROBERT C. WHITEHEAD JR.

BY i

ATTORN EY.

Feb. 17, 1959 R. c. WHITEHVEAD, JR ,87

AIR-PRESSURE-OPERATED RELAY Filed Jan. 11, 1954 2 Sheets-Sheet 2INVENTOR.

. m ROBERT c. WHITEHEAD JR. WA w ATTORNEY.

2,873,755 AIR-PRESSURE-OPERATED RELAY Robert C. Whitehead, Jr., Oreland,Pa., asslgnor to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation of Delaware Application January 1 1, 1954, SerialNmttisnis 5 Claims. 01. 137-85) The general object of thepresentinvention is to provide a new and improved apparatus forproducing a pneumatic signal which may be transmitted to some remotepoint, said signal being proportional in magnitude to the magnitude ofsome inputvariable. More specifically,

'Further, it is desirable that a linear relationship exist between theinput variable and the transmitted pressure so that the apparatus may bereadily adapted for use with standard types of pneumatic receivingapparatus. In addition, such apparatus should bestable and insensitiveto supply pressure changes so as to enhance the utility of theapparatus. v

The basic pneumatic apparatus of the present invention is of the jetforce balance type where the force is applied to a nozzle flapper andthis force is balanced by a reaction force caused by an air streamissuing from the nozzle striking the flapper. The nozzle back pressurewill vary in accordance with the air stream required to balance theinput force of the flapper unit. Apparatus of this general type will befound in the copending application of Frederick W. Side, Serial No.358,423, filed May 29,. 1953. The linearizing of apparatus of thepresent United States Patent 0 type has been found to be enhanced by theproper selection of the spring gradient of the resilient members used inthe apparatus and as a result it is essential that the apparatus beprovided with means for varying the spring gradient of the apparatuswithout appreciably affecting the other adjustments in the apparatus.The stabilizing of the apparatus may be accomplished by characterizingthe nozzle at its outlet and providing the air chamber for the nozzlewith a suitable stabilizing pneumatic impedance circuit.

It is therefore a more specific object of the present invention toprovide a new and improved pneumatic transmitting apparatus of the jetforce balance type having means for varying the spring gradient thereofto enhance the linearity of the apparatus.

7 A still more specific object of the present invention is. to provide anew and improved pneumatic transmitter of the jet balance type having acharacterized nozzle opening with said characterized opening providingstability for the transmitter.

Still another more specific object of the present invention is toprovide a stabilized jet balance pneumatic trans mitter having a nozzleoutput connection incorporating a stabilizing pneumatic impedancecircuit.

A further more specific object of the present invention is to provide anew and improved stabilized jet balance 2,873,755 Patented Feb. 17, 1959"ice pneumatic transmitter having a flapper unit with a pair of springsconnected thereto, one of said springs cooperating with other means toprovide a variable input force with the other of said springs providingmeans for varying the spring gradient of the apparatus to enhance thelinearity thereof.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its advantages, and specific objects attained with its use,-referenceshould be had to the accompanying drawings and descriptive matter inwhich there has been illustrated and described preferred embodiments ofthe invention.

Of the drawings:

Fig. 1 represents a diagrammatic showing of one form of the apparatus;

Figs. 2A, B and C are cross sectional views of preferred forms ofpneumatic nozzles for use in the apparatus; and

Fig. 3 is an exploded view of one particular form of v the pneumatictransmitter incorporating the principles set forth in Fig. 1.

Referring first toFig. 1, the numeral 10 represents a variable sensingelement, such as a temperature responsive bulb which will have an outputpressure proportional to the temperature condition in the area whereinthe bulb is located. The pressure connection ll'connects the bulb 10 toa base member 12, the latter of which has appropriate channels formedtherein to provide a pressure connection to a Bourbon spiral 13. Thefree end of the spiral 13 has a spring 14 connected thereto at 15. Theother end of the spring 14 is connected to a pneumatic flapper unit 16which is pivoted at 17. Also connected to the flapper 16 is a furtherspring 18, the latter of which has its lower end adapted for movement inan armately slotted member 19 which is fastened to a base member 20.

Cooperating with the opposite end of the flapper 16 is a nozzle member25 which has air supplied thereto by an input conduit 26 which passesair through a restriction 27. The restriction 27 is.connected to achannel block 28 which is a straight through connection for supplyingair to the nozzle 25 by way of a conduit 29. The back pressure from thenozzle 25 will be reflected through conduit 29 and a further conduit 30to a suitable pneumatic valve 31 which may be used in any desirablemanner to change the conditions which are affecting the magnitude of thevariable sensed by the bulb 10. It will be readily apparent that thepressure signal in the conduit 30 may also go to any type of pneumaticutilization device, such as an indicator, recorder, or the like.

Also connected to the block 28 in communication with the nozzle backpressure is a pneumatic impedance circuit including a capacity chamber32 which is connected to the block 28 by way of a resistance tubing 33.

Considering the operation of Fig. 1 it should first be noted that theBourdon spiral 13 will assume a position which is proportional to themagnitude of, the pressure applied thereto. This position will have theeffect of placing the spring 14 under stress so that there is applied tothe nozzle 16 a force which is proportional to the posi tion of the end15 of the spiral 13. As air is supplied to the nozzle 25 by way ofrestriction 27, there will be air issuing from the nozzle and this airwill strike the flapper unit 16 and create a reaction force which tendsto balance the input force applied to the flapper unit by the spring 14.For any one particular input force applied to the flapper unit 16 by thespring 14, there will be a corresponding jet reaction force to balancesaid input force. In order to achieve this balancing force, it isnecessary that the back pressure of the nozzle 25 vary 3 with thevariations in the input force. This variation is eflected by the flapper16 moving a minute distance toward the nozzle and the building up of theback pressureso that the higher back pressure will cause a larger forceto be exerted against the flapper to balance the flapper input force.

If a higher input pressure is applied to the spiral 13, the end'l' willdeflect upwardly and the spring 14 will cause a larger force to beapplied to the flapper unit 16. This larger force will be balanced by alarger jet reaction force produced by the back pressure of the nozzle 25increasing. The back pressure changes of the nozzle 25 will be reflectedthrough the conduit 36 to the valve 31 which will be repositioned inaccordance with the pressure change. The stabilizing of this backpressure is effected in part by the presence or" the pneumatic impedancecircuit including the resistance 33 and capacity chamber 32. Thisimpedance circuit tends to prevent high frequency fluctuations appearingat the nozzle from being reflected through the system and causing theoutput pressure to vary. Further, this tends to stabilize the supplypressure variations which also may tend to upset the output controllingaction in the apparatus.

As the linearity of this jet force balance type system is dependent inpart upon the spring gradient of the apparatus, the spring 18 has beenadded to provide means for varying the spring gradient so that thehighest degree of linearity may be obtained regardless of the type ofapparatus with which the transmitter may be used. The

spring gradient of the apparatus may be varied by shifting the end ofthe spring 18 in the arcuately slotted member 19 so that the neteffective gradient of the spring 18 in the apparatus will vary inaccordance with the angular displacement of the spring with respect toits connection to the flapper unit 16. Inasmuch as the flapper unit 16has no appreciable movement, the movement of the spring 18 will notappreciably affect the overall span or range of theapparatus.

It was found with one particular embodiment of the apparatus that themaximum linearity error was approximately five tenths percent over thefull span of the apparatus. As the spring gradient of the apparatus willvary with different types of Bourdon spirals and changes in theaccompanying size of the spring 14, it will be readily apparent that theadjustment provided for the spring 18 is essential in order that theappropriate spring gradient be provided to give maximum linearity.

The nozzle configuration shown in Fig. 2A has been found to contributemeasurably to the stability of this jet balance type of apparatus. Here,the nozzle 25 is shown to comprise a reduced section 35 which leads tothe opening of the nozzle. The opening of the nozzle 1as beencounter-sunk at 36 to provide a knife edge at the end of the nozzlewhere it is adjacent the flapper 16. in order that the nozzle be fullyeflective and not introduce non-linearities into this system, it isessential that the knife edge around the opening of the nozzle be freefrom any flat sections.

Fig. 2B shows one form of nozzle which has a sharp edge 37 adjacent thenozzle opening with a conical outer surface. This form of nozzle is lesssensitive to supply pressure changes and may be desirable wherestability is not a problem.

Fig. 2C shows a modified nozzle form which is a compromise between thefeatures found in Figs. 2A and 2B. Here, the nozzle is counter-bored at38 and has a sharp outer edge at 39. This form is more stable than thatof Fig. 2B and slightly more sensitive to supply pressure variations.

The apparatus shown in Fig. 3 is an exploded View of a pneumatictransmitter. Here, a variable sensing bulb 40 is connected to a suitableBourdon spiral 41 and is arranged to deflect the end of the Bourdonspiral at 42in accordance with the pressure changes within the sensingelement 40. The movement of the end 42 of asrayrse the spiral 41 may beapplied through a suitable rack 43 and pinion gear 44 to position anindicator needle 45 in accordance with the magnitude of the variablesensed by the unit 40. This entire assembly thus far set forth may befastened to the back side of a panel member 46, by means not shown.

The panel member 46 is arranged to enclose a chamber 47 formed on theback of the block 48, shown in cut and exploded view. The panel member46 has an opening 49 extending therethrough which cooperates with afurther opening 50 in the block 48. Thispermits the transmission of amotion signal to spring 51 produced by the movement of the end of theBourdon spiral 41 through the panel 46 and the block 48 to be utilizedin a manner hereinafter described.

The block 48 has an input conduit 52 which may be connected to asuitable supply of air under pressure. A conduit 52 is connected to twodrilled channels within the block '48. These channels include a channel53 which is connected to supply pressure to the supply pressuremeasuring instrument 54. A further channelr55 is connected to supply airto a restriction 56. The air flowing through the restriction passes to afurther channel 57 which is connected to supply air to the nozzle 58.Extending at right angles from the channel 57 is a further channel 60which extends towards the back of the block 48 and provides an openinginto the chamber 47. This opening will cooperate with the closed end 61of a molded channel 62 which is formed in the chamber 47. The channel 62provides a resistance connection into the chamber 47 and corresponds ineffect to the resistance tubing 33, shown in Fig. 1.

Also included in the block 48 are the output connections for theapparatus. This includes an output conduit 65 whichis connected todrilled channels in the block. One of these channels at 66 providesaconuection from the chamber 47 to the output conduit 65. A furtherchannel 67 provides a connection for an output pressure measuringinstrument 68.

Arranged to be movably mounted within the block 48 is a flapper member70 formed with three legs. An input leg 71 includes an adjustableelement 72 which is movable along the length of the leg 71 and aconnection 73 is provided for making a direct mechanical connection tothe spring 51 attached to the end of the Bourdon spiral 41. The leg 74comprises an adjultable member 75 which is used to vary the point ofconnection of a spring 76 to the leg 74, and therefore provide alinearity adjustment for the apparatus. The opposite end of the spring76 is carried by a pair of relatively adjustable members 77 and 78which'provide the zero adjustment for the apparatus. The further leg 80of the flapper unit 70 carries a flapper or vbaffle plate 81 which isformed at right angles to the flapper leg 88 with the leg 80 providing ashield to prevent interference with the action of the nozzle 58 againstthe flapper 81 when an appropriate cover, not shown, is placed over theend of the block 43. An appropriate fastening means 82 is provided forfastening the flapper unit 7% into position within the block 48, on theprojection 83. A further fastening means 84 is provided for fasteningthe zero adjusting levers 77 and 78 to an appropriate mountingprojection 85.

The apparatus of Fig. 3 operates in substantially the same manner as theapparatus of Fig. I. Here, an input pressure from the element 40willproduce a predetermined deflection of the Bourdon spiral 41 and thisdeflection will be reflected by way of the spring 51 into a force whichwill act upon the connector '73 of the flapper unit 70. This will causethe flapper to be rotated in a clockwise direction toward the nozzle 58.This input force will be balanced by a counterbalancing force'from thenozzle 58 caused by the air stream therefrom creating a reaction forceagainst the flapper 81. As soon as the reaction force equals the inputforce, a predetermined output pressure will exist in the channel 60 ofblock 48. This output pressure will be applied through the channel 62and will then pass into the chamber 47. The channel 62 and the chamber47 correspond to the resistance member 33 while the chamber 47corresponds to the capacity chamber 32 of Fig. l. The back pressure fromthe nozzle 58 will be reflected through this restricted passage 62 andthe chamber 47 and will then be applied to the output conduit 65 andthere to the control valve 31. It will be noted that this connectiondiflers somewhat from that of Fig. l in that the output connection isfrom the capacity chamber. It has been found that either method ofoutput is satisfactory in providing the desired stabilization.

In order to change the span ofthe apparatus, the adjustment 72 is movedto vary the point at which the input from the Bourdon spiral acts uponthe leg 71 of the flapper unit 70. In addition, the movement of theconnector 75 along the leg 74 has the effect of varying the linearity ofthe apparatus by varying spring gradient of the entire flapper system.In addition, the zero of the apparatus may be adjusted by adjusting therelative positions of the levers 77 and 78.

It will be readily apparent that changes in the input force from theBourdon spiral 41 will be effective to cause corresponding changes ofoutput pressure from the apparatus with the input force acting on theflapper unit 70 being balanced by the jet reaction force of the nozzle58 which strikes the flapper 81. This form of the apparatus has beenfound to be highly stable, linear, and adaptable to operation over wideranges of input forces.

While, in accordance with the provisions of the statutes, there has beenillustrated and described the best forms of the embodiment of theinvention known, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed Withoutdeparting from the spirit of the invention as set forth in the appendedclaims, and that in some cases certain features of the invention may beused to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A pressure transmitter comprising a Bourdon spiral having a pressureinput for deflecting one end thereof by an amount proportional to theinput pressure, an air-pressure-controlling valve comprising a flapperand a cooperating nozzle having an outlet air stream positioned tostrike said flapper and to create a reaction force on said flapper, afirst resilient member connected to said spiral at the deflecting endthereof and to said flapper and constituting the sole means for applyinga force from said spiral to said flapper, said force being proportionalto the deflection of the movable end of said spiral, a second resilientmember connected at one end to said flapper and at the other end to abase member which is fixed relative to said flapper, said secondresilient member creating a force onsaid flapper which is in oppositionto the force from said first resilient member, and means permittingadjustment of said second resilient member and for holding said secondresilient member in adjusted position.

2. Apparatus as defined in claim 1 wherein said pneumatic nozzle has itsopen end countersunk and has a supply chamber having a restricted airinlet thereto and an outlet comprising a further air restriction and acapacity chamber.

3. A pressure transmitter comprising a Bourdon spiral having a pressureinput for deflecting the end thereof by an amount proportional to thepressure input, a first resilient member connected to said spiral at thedeflecting end thereof, a pneumatic flapper having a force appliedthereto by said resilient member, said force being proportional to thedeflection of the end of said spiral, a second resilient memberconnected at one end to said flapper and at the other to a base memberwhich is fixed relative to said flapper, said second resilient membercreating a force on said flapper which is in opposition to the forcefrom said first resilient member, and a pneumatic nozzle having anoutlet air stream positioned to strike said flapper and create areaction force on said flapper to balance the net input force to saidflapper, said nozzle having a passage extending therethrough with theopening adjacent said flapper being formed with a diameter larger thansaid passage.

4. Pneumatic apparatus comprising, a pivoted flapper, means for applyingan input force to said flapper, a spring member fastened to said flapperand adjustably attached for angular movement relative to said flapperand to a base member for varying the spring gradient of said apparatus,and a pneumatic nozzle cooperating with said flapper, said nozzle havingair issuing therefrom and striking said flapper to create a reactionforce which will balance the input force on said flapper and having acounterbored opening adjacent to said flapper.

5. A pressure transmitter comprising a Bourdon spiral having a pressureinput for deflecting the end thereof by an amount proportional to thepressure input, a first resilient member connected to said spiral at thedeflecting end thereof, a pneumatic flapper having a force appliedthereto by said resilient member, said force being proportional to thedeflection of the end of said spiral, a second resilient memberconnected at one end to said flapper and at the other to a base memberwhich is fixed relative to said flapper, said second resilient membercreating a force on said flapper which is in opposition to the forcefrom said first resilient member, and a pneumatic nozzle having anoutlet air stream positioned to strike said flapper and create areaction force on said flapper to balance the net input force to saidflapper, said pneumatic nozzle having its open end countersunk andhaving a supply chamber having a restricted air inlet thereto and anoutlet comprising a further air restriction and a capacity chamber.

References Cited in the file of this patent UNITED STATES PATENTS1,799,131 Frymoyer Mar. 31, 1931 2,212,085 Tate Aug. 20, 1940 2,299,884Edwards Oct. 27, 1942 2,399,938 Pett May 7, 1946 2,612,902 Ward Oct. 7,1952 2,618,288 Catheron Nov. 18, 1952 2,626,626 Rosenberger et al Ian.27, 1953 2,652,066 Bowditch Sept. 15, 1953 FOREIGN PATENTS 562,645 GreatBritain 1944 604,468 Great Britain 1948 900,424 France 1944

